MINERALS: A TEACHER’S COMPREHENSIVE GUIDE TO MACRO-MINERALS AND MICRO-MINERALS
Welcome, future healthcare professionals!
Minerals are inorganic elements essential for various physiological functions in the human body. They mostly form complexes with insoluble fibres or phytates in the intestine, which hinders the intestinal absorption of dietary minerals, except for sodium and potassium. Few minerals are found in free and unbound form in blood circulation, while some are transported with the help of specific binding proteins (e.g., transferrin for iron). Specific binding proteins are required to store minerals (e.g., for storing iron, apoferritin protein is needed).
Dpharmguru’s exam insights:
In my years of teaching biochemistry and nutrition, I have observed that students often get confused between macro-minerals and micro-minerals. Remember: Macro-minerals are required in amounts greater than 100 mg per day, while micro-minerals (trace minerals) are required in amounts less than 100 mg per day. This distinction is frequently tested in exams!
TYPES OF MINERALS
- Macro-minerals or Essential or Major Minerals: The daily requirement of these minerals is more than 100 mg per day. Examples include Sodium, Potassium, Calcium, Chloride, Magnesium, and Phosphorus.
- Micro-minerals or Trace Minerals: The daily requirement of these minerals is less than 100 mg per day. Examples include Iodine, Fluorine, Copper, Cobalt, Manganese, Iron, Zinc, etc.
PART 1: MACRO-MINERALS
1. Calcium
Calcium is a chief constituent of bones and teeth. In blood, half of the calcium is found in ionised form and the rest in unionised form. A part of the unionised calcium is bound to citrate and some is bound to protein. Calcium is consumed in the diet in the form of calcium phosphate or carbonate.
Functions of Calcium:
- Bone Calcification: Calcium is required for the calcification of bones and teeth.
- Blood Coagulation: It plays a significant role in the coagulation of blood as it helps in the conversion of prothrombin to thrombin and in the synthesis of thromboplastin.
- Action of Enzymes: It acts as an activator for many enzymes (e.g., lipase, succinic dehydrogenase, ATPase, and some proteolytic enzymes).
- Contraction of Muscle: Calcium ions help in muscle contraction by neutralising the negative charge of myosin which further combines with actin. Calcium ions activate the myosin ATPase enzyme which hydrolyses ATP, thus providing energy for muscle contraction.
- Excitability of Neuromuscular: It is required for nerve excitation.
- Hormone Action: It acts as an intracellular secondary messenger of different hormones.
- Hormone Release: It facilitates the release of certain hormones, such as insulin, PTH, and calcitonin.
- Membrane Permeability: It increases the permeability of plasma membrane, and thus the effect is counterbalanced by the opposite action of sodium and potassium capillary permeability.
Deficiency Diseases of Calcium:
- Rickets: A condition that affects bone development in children. It causes pain in bones, poor growth, and soft and weak bones that can lead to bone deformities. Adults experience a similar condition, known as osteomalacia or soft bones.
- Osteoporosis: A condition which causes bones to become weak and brittle so that a fall or even mild stresses such as bending over or coughing can cause a break. Such breaks most commonly occur in the hip, wrist, or spine.
- Osteopenia: A condition of decreased bone mineral density which occurs when an individual receives inadequate calcium for a long period. This condition leads to osteoporosis if ignored.
- Other Deficiency Symptoms: Muscle cramps, numbness, tingling of fingers, fatigue, poor appetite, and irregular heart rhythms.
Recommended Dietary Requirement and Dietary Sources: Around 0.5 g/day of calcium is required for a healthy adult man; about 1.5 g and 1.0 g per day for pregnant women and children, respectively. The chief sources of calcium are milk, eggs, fish, and vegetables. Cereals (wheat and rice) also contain a small amount of calcium.
Dpharmguru’s exam insights:
A common exam question is: “What is the difference between rickets and osteomalacia?” Remember: Rickets occurs in children (growing bones), while osteomalacia occurs in adults (softening of bones). Also, osteoporosis means “porous bones” and is more common in postmenopausal women due to decreased estrogen.
2. Phosphorus
Phosphorus is one of the major components of bones and helps in bone mineralisation. It is also used for the production of energy. In a healthy adult, phosphate concentration is about 1 kg, 80% of which is present in bone and teeth, while 10% is in muscles.
Functions of Phosphorus:
- Formation of Bones and Teeth: After calcium, phosphorus is the major constituent of bones and teeth.
- Production of High Energy Phosphate: It is required for the production of high-energy phosphates, like ATP, CTP, GTP, etc.
- Formation of Nucleic Acid: The backbone of DNA and RNA is formed of phosphate diester linkages.
- Activation of Enzymes: Phosphorylation helps in the activation of some enzymes.
- Production of Biochemical Compounds: Phosphate is also required for the formation of various biochemical compounds, like phospholipids, phosphoproteins, lipoproteins, and nucleotides.
Deficiency Disease: The deficiency of phosphorus leads to hypophosphatemia. It can be caused by decreased absorption of phosphate, intracellular shift, increased urinary excretion of phosphate, hereditary hypophosphatemia, hypercalcaemia, chronic alcoholism, and drugs (e.g., antacids, diuretics, and salicylate intoxication).
Recommended Dietary Requirement and Dietary Sources: Around 500 mg/day of phosphate is required for a healthy adult man; about 1 g and 400-600 mg per day for pregnant women and children, respectively. Chief sources of phosphate are cheese, milk, nuts, eggs, etc.
3. Sodium
Sodium is the chief cation of the extracellular compartment. Around 50 mmol/kg body weight of sodium is found in the body of a healthy adult man. Sodium concentration in plasma is about 135-145 mmol/litre.
Functions of Sodium:
- Neuromuscular Excitability: Sodium together with potassium cations increase neuromuscular excitability.
- Regulation of Fluid: Being major cations of extracellular fluid, they are actively involved in maintaining the osmotic pressure.
- Acid-Base Balance: Sodium is the element of the bicarbonate buffer system in the form of sodium bicarbonate salt.
- Membrane Transport: Active absorption of various substances across the plasma membrane occurs through sodium co-transport.
Deficiency Diseases:
- Hyponatraemia: A condition of decreased sodium levels in the body. Serious hyponatremia may cause seizures, coma, and even death.
- Electrolyte Imbalance: A severe sodium imbalance can lead to spontaneous seizures or prolonged epileptic seizures.
- Dehydration: A condition in which body levels of sodium are decreased. Fluids leave the body through sweating, urination, and in the vapor that is breathed out from the lungs.
Recommended Dietary Requirement and Dietary Sources: Around 5-10 gram of sodium is present in a normal Indian diet in the form of table salt (sodium chloride), meat, fish, eggs, milk, cheese, cauliflower, spinach, legumes, and nuts. In a tropical country like India, the daily requirement of sodium is around 5-6 grams. Excessive consumption of sodium causes hypertension.
Dpharmguru’s exam insights:
Sodium is the major extracellular cation, while potassium is the major intracellular cation. Remember: “Sodium = Outside, Potassium = Inside.” This is a common exam question! Also, excessive sodium intake leads to hypertension, a major risk factor for cardiovascular disease.
4. Potassium
Potassium is the major intracellular cation and is generally found in tissues and body fluids. It plays a critical role in various physiological processes, including nerve function, muscle contraction, and fluid balance.
Functions of Potassium:
- Maintains acid-base balance.
- Helps in proper functioning of cardiac muscles and the muscular system.
- Regulates enzymatic actions, e.g., pyruvate kinase needs K+ as a cofactor.
- Helps in neurotransmission.
Deficiency Diseases: Potassium deficiency is mainly caused due to excessive fluid loss (like extended vomiting), kidney disease, or use of medications (like diuretics). The symptoms of potassium deficiency are muscle cramping, weakness, constipation, bloating, or abdominal pain caused by intestinal paralysis. Severe potassium deficiency can cause muscle paralysis or irregular heart rhythms that might be fatal.
Recommended Dietary Requirement and Dietary Sources: A healthy adult human requires around 2.4 grams of potassium, while a child requires around 1.3 grams. It is widely present in vegetables.
5. Chloride
Chloride is the chief anion in the body. Generally, normal serum chloride levels undergo parallel alterations with sodium levels. Around 125 mmol/litre chloride is found in the CSF, which is more than in any other body fluid.
Functions of Chloride: Chloride ions regulate osmotic pressure of extracellular fluids along with sodium cations. They help in the synthesis of hydrochloric acid in the stomach and also maintain blood pH.
Deficiency Disease: Hypochloraemia (decreased chloride concentration) occurs due to severe vomiting or loss of HCl, Addison’s disease, prolonged gastric suction, and respiratory acidosis and metabolic alkalosis.
Recommended Dietary Requirement and Dietary Sources: An average adult requires around 5-10 grams of chloride daily. The chief sources are table salt (NaCl) and foods like meat, fish, cheese, cereals, eggs, etc.
6. Magnesium
A healthy adult contains around 25 grams of magnesium; around 70% is found in the skeleton, around 30% in liver, muscle (soft tissues) and body fluids, and only 1% in blood and ECF.
Functions of Magnesium:
- Enzyme Activator: Magnesium activates many enzymes, especially those in which the substrate is a complex of ATP and magnesium.
- Neuromuscular Excitability: It is decreased by high concentration of magnesium ions; while low concentration increases nerve excitability.
- Glucose Tolerance: It is improved in the presence of magnesium ions as insulin-dependent glucose uptake is increased.
- Others: Magnesium is needed for DNA replication, transcription, and translation. It also binds to nucleoside phosphate and nucleic acids.
Deficiency Diseases: Fatigue, weakness, appetite loss, nausea, and vomiting are the early signs of magnesium deficiency. If the condition is not treated, numbness, tingling sensations, muscle cramps, seizures, and abnormal heart rhythms occur.
Recommended Dietary Requirement and Dietary Sources: Around 350 mg/day of magnesium is needed for a healthy adult man; about 300 mg and 150-250 mg per day for adult women and children, respectively. Chief food sources are nuts, cereals, beans, fish, almonds (rich source), and leafy green vegetables.
PART 2: MICRO-MINERALS
1. Iron
Iron is significant for many proteins and enzymes (particularly haemoglobin). Around 3-5 g iron is found in a healthy adult human body; 75% is present in blood in the form of haemoglobin, 5% in myoglobin, and 15% in ferritin.
Functions of Iron:
- Helps to oxygenise the blood.
- Helps to convert blood sugar into energy.
- Boosts the immune system.
- Aids cognitive function.
- Maintains healthy skin, hair and nails.
Deficiency Diseases: Iron deficiency gradually progresses and causes anaemia. Feeling weak and tired are the symptoms of iron-deficiency anaemia.
Recommended Dietary Requirement and Dietary Sources: Around 20 mg of iron is required per day for a healthy adult man; about 40 mg and 20-30 mg per day for pregnant women and children, respectively. The chief sources are leafy vegetables, pulses, cereals, liver, meat, and jaggery.
Dpharmguru’s exam insights:
Iron deficiency anaemia is the most common nutritional deficiency worldwide. Remember: Haemoglobin contains iron, and ferritin is the storage form of iron. A common exam question is: “Which protein transports iron in the blood?” The answer is transferrin.
2. Iodine
Iodine is a non-metallic trace element and helps in the synthesis of T3 (triiodothyronine) and T4 (thyroxine) thyroid hormones.
Functions of Iodine:
- Essential for the synthesis of thyroid hormones.
- Helps to reduce the risk of goitres.
- Helps to manage overactive thyroid gland.
- Promotes the health of thyroid gland.
- Useful in the treatment of thyroid cancer.
Deficiency Disease: Iodine deficiency causes stillbirths, abortions, congenital heart anomalies, endemic cretinism, mental retardation, and neurological defects. Treatment of iodine deficiency before pregnancy prevents disorders in children.
Recommended Dietary Requirement and Dietary Sources: Seafood is rich in iodine because they can concentrate iodine from seawater. Some seaweed (e.g., Undaria pinnatifida or wakame) are also very rich in iodine.
3. Fluorine
Fluorine helps in the formation of tooth enamel (highly mineralised part of the tooth that protects it from degradation), containing fluoroapatite.
Functions of Fluorine:
- Tooth Development and Dental Health: Essential for teeth development. Prevents dental caries. In large amounts, it causes fluorosis or mottling of the enamel.
- Bone Development: Enhances calcium and phosphate retention, thus promotes bone development and prevents old age osteoporosis.
Recommended Dietary Requirement and Dietary Sources: Around 10-20 mg of fluorine is found in the blood in its ionised form. Main sources are drinking water, tea, salmon, and sardine. About 1-2 ppm of fluorine is required per day.
4. Zinc
Zinc is pervasive in nature and is essential for many enzymes (carboxypeptidase, liver alcohol dehydrogenase, and carbonic anhydrase) to complete their metabolic processes.
Functions of Zinc:
- There are around 300 zinc-containing enzymes (e.g., lactate dehydrogenase, carbonic anhydrase, alkaline phosphatase, and carboxypeptidase).
- Found in cytosolic superoxide dismutase which contains copper also.
- Helps in the production of DNA and proteins.
Deficiency Diseases: Loss of appetite, taste or smell, decreased function of immune system, and retarded growth. Severe zinc deficiency causes diarrhoea, hair loss, impotence, and prolongs wound healing.
Recommended Dietary Requirement and Dietary Sources: Around 2.3 g zinc is found in the body. Chief sources are meat, liver, seafood, eggs, vegetables, and whole grams. Around 5 mg of zinc is required per day for a pregnant woman.
5. Cobalt
Cobalt is significant for the biosynthesis of vitamin B12 family of coenzymes. The total body content of cobalt is around 1.1 mg. It is mainly absorbed from the small intestine.
Functions of Cobalt:
- Constituent of vitamin B12 (around 4% of cobalt present). Also required for the production of haemoglobin.
- Causes polycythaemia by either increasing or preventing the destruction of erythropoietin hormone.
Deficiency Disease: Cobalt deficiency indicates vitamin B12 deficiency which causes pernicious anemia. Symptoms include numbness, severe tiredness (fatigue), and tingling in hands and feet.
Recommended Dietary Requirement and Dietary Sources: The average adult intake of cobalt is 5 to 8 mcg per day. The main sources are figs, cabbage, lettuce, spinach, and animal products like liver and kidney.
6. Copper
Copper is an important component of many redox enzymes (including cytochrome-c-oxidase). In the body, copper exists in two forms, i.e., cuprous and cupric.
Functions of Copper:
- Aids your body’s production of red blood cells while also maintaining the health of your nerve cells and immune system.
- Contributes to the formation of collagen, which is an important component of bones and connective tissue.
- Helps the body absorb iron.
Deficiency Diseases: Copper deficiency is rare and causes both haematological and neurological disease. Neurological diseases include myelopathy, peripheral neuropathy, and optic neuropathy.
Recommended Dietary Requirement and Dietary Sources: Copper should be consumed in an amount of 2 mg/day. The chief sources are organ meats, shellfish, nuts, seeds, wheat bran cereals, and whole grain products.
7. Manganese
Manganese acts as a cofactor of antioxidant enzymes (superoxide dismutase).
Functions of Manganese:
- Role in Animal Reproduction: Deficiency causes sterility in animals and disturbance in citric acid cycle.
- Proteoglycan Synthesis: Promotes synthesis and deposition of proteoglycans in many tissues.
- Porphyrin Synthesis: Constituent of some porphyrins of erythrocytes.
- Bone Growth: Required for bone growth and cholesterol synthases.
- Acts as Cofactor: For enzymes like arginase, isocitrate dehydrogenase, and leucine aminopeptidase.
Deficiency Diseases: Manganese deficiency is rare but may cause bone demineralisation and poor growth in children, skin rashes, hair depigmentation, decreased serum cholesterol, and increased alkaline phosphatase activity.
Recommended Dietary Requirement and Dietary Sources: Around 30 mg manganese is found in a healthy adult human body. Chief sources are cereals, vegetables, tea, liver, kidney, and muscle. Around 2-5 mg of manganese is required per day for a healthy adult.
8. Molybdenum
Molybdenum is necessary for xanthine oxidase and other related oxidases. However, deficiency of molybdenum has not been yet observed in humans.
Functions of Molybdenum:
- Takes part in uric acid metabolism.
- Involved in the action of various enzymes (aldehyde dehydrogenase and xanthine oxidase).
- In trace amounts, it helps in the utilisation of copper, whereas in larger amounts it diminishes the same.
Recommended Dietary Requirement and Dietary Sources: Chief sources are milk, beans, breads, cereals, liver, and kidney. Around 0.15-0.5 mg of manganese is required per day for a healthy adult.
9. Selenium
Selenium is necessary for peroxidase (antioxidant proteins).
Functions of Selenium:
- Integral part of glutathione peroxidase which guards vital cell components.
- Releases vitamin E and helps in its retention in the blood.
- Reduces the risk of certain cancers.
- Helps in purine metabolism (thioredoxin reductase).
- Helps in sperm motility and muscle metabolism in the form of selenoproteins.
Deficiency Diseases: Conditions associated with severe selenium deficiency are Keshan disease (cardiomyopathy) and Kashin-Beck disease (osteoarthritis).
Recommended Dietary Requirement and Dietary Sources: Around 5-15 mg selenium is found in the total body. Chief sources are liver, kidney, seafoods, meats, and grains. Around 0.2 mg of selenium per day is required for a healthy adult.
10. Sulphur
Sulphur acts as an enzyme cofactor and is an essential component of cysteine and methionine. Amino acids containing sulphur are important constituents of body proteins.
Functions of Sulphur:
- Used in the formation of amino acids, proteins, and oils.
- Necessary for chlorophyll formation, promotes nodulation in legumes.
- Structural component of two of the 21 amino acids that form protein.
Deficiency Diseases: A deficiency of sulphur can cause acne, arthritis, brittle nails and hair, convulsions, depression, eczema, itchy skin or scalp, migraine headaches, memory loss, gastrointestinal issues, rashes, and slow wound healing.
Recommended Dietary Requirement and Dietary Sources: The recommended daily intake of sulphur is about 850 mg per day. The main dietary sources include allium and cruciferous vegetables, animal proteins, dairy, legumes, nuts, and seeds.
Dpharmguru’s exam insights:
Understanding minerals is essential for understanding nutrition, metabolism, and disease prevention. In exams, pay special attention to: (1) The difference between macro and micro minerals, (2) The functions and deficiency diseases of each mineral, and (3) The recommended dietary allowances. Remember: “Minerals are the building blocks of health – know them well!”
REFERENCES AND FURTHER READING
- Park, K. (2022). Park’s Textbook of Preventive and Social Medicine (26th ed.). Banarsidas Bhanot Publishers.
- Murray, R. K., Bender, D. A., Botham, K. M., et al. (2018). Harper’s Illustrated Biochemistry (31st ed.). McGraw-Hill.
- World Health Organization (WHO). (2022). Trace Elements in Human Nutrition and Health. Retrieved from https://www.who.int.
- National Institutes of Health (NIH). (2022). Minerals and Nutrition Resources. Retrieved from https://www.nih.gov.
- Indian Council of Medical Research (ICMR). (2022). Nutrient Requirements and Recommended Dietary Allowances for Indians. New Delhi: ICMR.
Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals for medical concerns.
written by:
Dr. N. Sujith Kumar
